The invention relates to a towing arrangement or hitch for prime movers, in particular for coupling implements with tow bars to an agricultural or utility vehicle.
Agricultural or utility vehicles, in particular, such as agricultural tractors, frequently contain a hitch so that implements can be coupled to and towed by the tractor. For this purpose a towing hook is provided on the prime mover, which is able to engage a clevis in the tow bar of the implement. For tow bars that must be raised from the ground for the coupling process there is an advantage in attaching the towing hook on the utility vehicle so as to be adjustable in height, so that the prime mover can be backed up and the towing hook engaged with the clevis of the tow bar, in order to perform the coupling process. After coupling the towing hook to the tow bar, the towing hook and the tow bar are lifted by a mechanical arrangement.
Certain standards must be observed in the case of tractors with power take-off shafts. For example, the ISO 500/6489 standard requires a fore-and-aft spacing distance of 100 millimeters between the towing hook and the end of the power take-off shaft. This means that the coupling point is located relatively close to the rear of the vehicle cab and is not always visible from the operator's seat, in particular when it is in its lower position. It would be desirable to simplify the coupling process by improving visibility of the coupling point.
In German patent reference DE 1 249 099, a coupling arrangement for tractors is shown in which two levers are arranged under the tractor body, each of which is pivoted at one end about a pin on the tractor body. A towing hook is provided at the other end of each lever. These levers can be raised and lowered by means of a lift shaft, lift arms, chains and drawbar. Thus, the towing hooks move in a circular arc about the axis of the pins. In the lowered position, the towing hooks are located close to the rear of the tractor and are not visible from the operator's seat.
Another similar hitch is shown in European Patent publication EP 0 184 489. In this known hitch the towing hook is pivotally coupled to the vehicle chassis by a pair of spaced apart pivoting links. One link is coupled to the forward end of the towing hook and the other link is coupled to a central portion of the towing hook. The two links determine the curved path through which the towing hook moves as it is raised and lowered. The towing hook is raised by a lifting arrangement which includes a telescoping rod that is attached to a lift rod in the vicinity of the towing hook.
In this hitch the lift lever is located below the vehicle body and thereby reduces the ground clearance of the vehicle. Furthermore, in this location the arrangement is subject to an increased danger of dirt accumulation during operation. Because in its lowered position the towing hook extends further beyond the rear of the tractor than in its locked position, it may, therefore, be visible from the operator's seat in its lowered position. However, during lifting the towing hook is rapidly retracted and disappears from the operator's visual field. That means that the operator is able to capture the clevis of the tow bar only with considerable difficulty when the tow bar is not in the lowest position of the hitch.